From Sweden - According to a study published in BMJ Open, an air pollutant may be responsible for a significant amount of preeclampsia cases. Researchers studied over 120,000 births in Sweden between 1998-2006. They also reviewed mothers exposure to the air pollutants ozone and vehicle exhaust (nitrogen oxide), as well as their asthma status. Results showed no association between preeclampsia and vehicle exhaust, as well as no association between air pollutants and children underweight at birth. However, researchers did find that exposure to ozone in the first three months of pregnancy raised risk of preeclampsia and premature birth. Researchers estimate that ozone exposure may account for 1 in 20 cases of preeclampsia.